Here is the feedback of Xav in the beta offical forums for anyone that missed it :
"Naxxramas 25 man
Premonition and Vis Maior joint raid, everyone at least fully sunwell geared, many people with gear already from the 10-man Naxx, heroics, crafted, or level 80 five mans/heroics. All tanks were crit immune.
Standard raid comp was
1 Prot warrior
1-2 Fury warriors
1 Ret paladin
0-1 Prot paladin
1-2 Holy paladin
2-3 Resto shaman
0-1 Enhance shaman
1 Elemental shaman
1 Feral druid
1 Resto druid
2 Holy priest
1 Shadow priest
1 Unholy DK
1-2 Blood DK
0-1 Frost DK
1 Frost Mage
2 Arcane Mage
1 Mutilate Rogue
2 Survival hunters
1 BM hunter
2 Destro Warlocks
0-1 Affliction Warlock
Spider Wing
Anub'rhekan
Easy, Locust Swarm even functioning? Didn't notice taking 'magical' damage in my blizzard scrolling combat text the one time I got several stacks of it. (Ground spike/impale thing shot me in the air right before he started casting it, so I wasn't able to start moving until it was basically mid cast)
Grand Widow Faerlina
Easy, everything seems to work as intended in the fight, pretty much the same as the 60 version with the mind controls, RoF, poison, and so forth. Didn't notice nearly as much raid damage as I was accustomed to seeing at level 60, however.
Maexxna
Easy, we stopped dps at 32%, waited for a web spray, and then used hero. Burned her down and used timers to live through the enrage, not sure if I would have even died though even if shield wall wasn't up. Didn't seem like a threat at all, to anyone, in the whole fight.
Spider wing trash:
Very easy, can pretty much group up everything and AOE it down. We pulled three of the Cultist packs in Faerlina's room and aoed it all down together without any deaths. However, that is considerably better than how tedious Faerlina trash was in Naxx 1.0 @ 60.
Plague Wing
Noth the Plaguebringer
Easy, was not doing blinks in the first ground phase at all, so it was simply a tank and spank. The curse is applying to so few people that it's a non-factor in the fight. The add phase where he goes up on the balcony is easy as well, we simply offtanked all the adds from phase 1, then aoe'd them in addition to the waves coming in during phase 2. His secound ground phase he finally started blinking, but only got one off before dying.
Heigan the Unclean
Easy, but mostly because his dance was slowed down so much! There's no more teleportation, which is understandable for the 10 man, but in the 25 man it's kind of depressing. I think you should still be teleported even in the 25 man now, it's not hard or anything, it just adds something different to the fight now and then for some people. As long as you fixed the unavoidable deaths with being ported right before a dance phase from Naxx 1.0
Loatheb
Very easy, health seems far too low, I think we ate two or three impending dooms total? New mechanic is fine, simplifies things/learning. It should probably be a bit more dangerous for the raid when he dies rather than everyone completely healthy, in my opinion anyway.
Plague wing trash:
The Gargoyles and all the rest of the pre-Noth trash is fine. The old gauntlet, now the non-respawning trash, is fine, but pointlessly easy. And what's with the jumping bats? The bats... jump on you. I don't understand that.
Abomination Wing
Patchwerk
Ridiculously undertuned! I think we killed him with like over a minute left on the timer, but I dont have an exact time because the screenshot I took was taken with my timer still running. I remember saying on vent, "we're way way ahead" sometime during the fight, knowing it was a 5 minute enrage. Damage to the main tank is fine - could be upped a little bit, and damage from Hateful Strike seems WAY too low. It wasn't a rollercoaster ride like it was @ 60, I don't think hatefuls even brought them below 50% hp.
Grobbulus
Not bad at all. Same exact concepts, but just health values/damage tuned up. Sometimes when he turns to face the raid to inject someone, he does the Slime Stream at the same time and multiple slimes will spawn, this seemed completely unavoidable due to the timing of it. Ranged were on spawns and melee stuck on the boss, seems like it will be a good fight for a lesser geared raid.
Gluth
Bugged. After decimate, the zombie chow are NOT aggroed on Gluth and continue to attack the kiters, the healers, or the DPS aoe'ing them down. Thus, our strat was to AoE Taunt/earth elemental, and then we decided to simply just continue to kite them after decimate since they were not converging on Gluth. He is not tauntable, and the Mortal Wound he applies does not function. I would solo tank him, get to a 10 stack, and then it would wear off. If the mortal wound is fixed and he remains untauntable, due to there being no fear mechanic this could be quite an interesting fight. Not sure how to swap aggro reliably without a fear, in sufficient time, to not die to mortal wound. Might end up doing "clever" things like using timers + intervene shield wall effect + trinkets / tricks to live through a high stack of mortal wound, waiting for it to tick off. (Doesn't refresh at 10stack)
Thaddius
Phase 1 change is nice, the way you fly directly to the other tank without the actual positioning difficulties of Naxx 1.0. Phase 2 is identical and I don't know how far ahead we were because I don't know what the enrage is, however, we had like 3 deaths and we were fine.
Abomination Wing trash:
The reduction of trash before Patchwerk is nice, but I think the lightning totems should inflict more pain to encourage people to actually kill them rather than ignore them!
Death Knight Wing
Instructor Razuvious
Returning to the mind control strategy is appreciated. The adds, however, have a mind of their own. Our first strategy was just me tanking all of the adds in a spot that the priests can MC them easily at, but they would frequently just run away from me and go to healers. (And it was *NOT* due to them pulling aggro). Frequently after taunting it back, off a healer, and slamming a HUGE amount of threat into it seconds after the taunt, it would immediately run back to the healer. This ended up wiping us. Our next attempt we used 4 tanks, each tank assigned to one of the adds, and we baby sat our own adds. It worked fine and aggro was not squirrely at all this way - not sure why, but yeah.
Gothik the Harvester
Hard. A true challenge, this was just like the 60 version for the most part. We wiped many times, even after knowing what to do. We were using 3 shackles and 3 sheeps, and frost novas + 2 tanks on each side to control all adds. All Rider volleys were interrupted, and damage was still rough at times due to loose adds and being overran. I can see this easily being very, very difficult for new guilds to the zone seeing it for their first time.
4 Horsemen
Easy. Identical to the 10 man version, with numbers just tuned a bit higher. I was looking forward to mechanics being changed in some way from the 10 man to force more tanks into the fight, or more diverse rotations - right now it was just a 'front 2' swap with tanks meeting in the middle and taunting, then going to the other side with all of their healers/dps. Also, rogues can cloak the marks, and you can resist the marks, which makes it even easier. This should be scaled up considerably and more things added, if it's meant to be more difficult than Gothik.
Death Knight wing trash:
Tons of trash. Trash is annoying, too, with the Death Knight whatevers that do the whirlwind. Pats that patrol very very long distances and can sync up and travel together in huge deathpacks. (The invisible spectre pats would sync up with a death knight pack and cause a huge pull). Trash wont be bad if the pats were in smaller areas and easier to discern where they travel from, right now it's easy to get big chain pulls due to far aggro ranges.
Sapphiron
Pretty significant raid healing required. Sapphiron was shooting 2 Frostbolts (turning into iceblocks) for several air phases, forcing us to all be on one side (to survive reliably, anyway). Not seeing Sapphiron's cast bar/channel bar for Ice Blast or whatever it is called is awkward, but not a big deal. On later air phases (when she got lower health), she started shooting multiple frostbolts - I think we got 3, and then maybe 4? Nicely tuned, hits very hard, stresses healers, etc.
Kel'Thuzad
Phase 1 seems bugged, the adds are travelling veryveryvery slow, after doing the 10 man, which had them move fast and appropriately, the 25 man having them move literally at a snails pace is dumb. Fix their speed, make them move faster.
Phase 2 is ok, no idea why you don't add more abilities in though. It's a replica of the 10 man. Should put Detonate Mana back in, and maybe the Mind Control too - but have it not mind control anyone currently tanking a mob. Perhaps disable the mind control once 40% hits, that way you wont have to deal with mind control on add tanks, which seems appropriate for the difficulty level intended. You just need to spice this up a bit because it's a snore right now, lots of health, long fight, for most of the raid it is nothing more than press your button and move if a void zone is on you. However, making the Frostbolt still threatening enough to force an interrupt rotation is nice. It hit me for 16,666 - the one I got hit by, so you definitely need a strict solid rotation for that.
The soft enrage seems to be on the Guardians of Icecrown, as they hit harder and harder, (Their self buff now auto stacks based on time rather than deaths) causing your OT's to eventually probably die.
Overall: I like it, but it was easy, probably due to our experience/gear level. However, some of it is very obviously too easy and needs to be buffed. A few changes here and there and it'll be a great entry level zone with appropriate difficulty scaling as you work through the 15 bosses.
Thanks Blizzard "